A Microfluidic Immunostaining System Enables Quality Assured and Standardized Immunohistochemical Biomarker Analysis

Acoustofluidic large-scale mixing for enhanced microfluidic immunostaining for tissue diagnostics

The usage of microfluidics for automated and fast immunoassays has gained a lot of interest in the last decades. This integration comes with certain challenges, like the reconciliation of laminar flow patterns of micro-scale systems with diffusion-limited mass transport. Several methods have been investigated to enhance microfluidic mixing in microsystems, including acoustic-based fluidic streaming. Here, we report both by numerical simulation and experiments on the beneficiary effect of acoustic agitation on the uniformity of immunostaining in large-size and thin microfluidic chambers. Moreover, we investigate by numerical simulation the impact of reducing the incubation times and the concentrations of the biochemical detection reagents on the obtained immunoassay signal. Finally, acoustofluidic mixing was successfully used to reduce by 80% the incubation time of the Her2 (human epidermal growth factor receptor 2) and CK (cytokeratins) biomarkers for the spatial immunostaining of breast cancer cell pellets, or reducing their concentration by 66% and achieving a higher signal-to-background ratio than comparable spatially resolved immunostaining with static incubation.

The VersaLive platform enables microfluidic mammalian cell culture for versatile applications

Microfluidic-based cell culture allows for precise spatio-temporal regulation of microenvironment, live cell imaging and better recapitulation of physiological conditions, while minimizing reagents’ consumption. Despite their usefulness, most microfluidic systems are designed with one specific application in mind and usually require specialized equipment and expertise for their operation. All these requirements prevent microfluidic-based cell culture to be widely adopted. Here, we designed and implemented a versatile and easy-to-use perfusion cell culture microfluidic platform for multiple applications (VersaLive) requiring only standard pipettes. Here, we showcase the multiple uses of VersaLive (e.g., time-lapse live cell imaging, immunostaining, cell recovery, cell lysis, plasmid transfection) in mammalian cell lines and primary cells. VersaLive could replace standard cell culture formats in several applications, thus decreasing costs and increasing reproducibility across laboratories. The layout, documentation and protocols are open-source and available online at https://versalive.tigem.it/.

VersaLive is a versatile microfluidic platform with flexible input modes and low-volume media reservoirs that can be used for time-lapse live cell imaging, immunostaining, cell recovery, cell lysis and plasmid transfection.

Rapid detection of microorganisms in a fish infection microfluidics platform

Inadequate access to clean water is detrimental to human health and aquatic industries. Waterborne pathogens can survive prolonged periods in aquatic bodies, infect commercially important seafood, and resist water disinfection, resulting in human infections. Environmental agencies and research laboratories require a relevant, portable, and cost-effective platform to monitor microbial pathogens and assess their risk of infection on a large scale. Advances in microfluidics enable better control and higher precision than traditional culture-based pathogen monitoring approaches. We demonstrated a rapid, high-throughput fish-based teleost (fish)-microbe (TelM) microfluidic-based device that simultaneously monitors waterborne pathogens in contaminated waters and assesses their infection potential under well-defined settings. A chamber-associated port allows direct access to the animal, while the transparency of the TelM platform enables clear observation of sensor readouts. As proof-of-concept, we established a wound infection model using Pseudomonas aeruginosa-contaminated water in the TelM platform, where bacteria formed biofilms on the wound and secreted a biofilm metabolite, pyoverdine. Pyoverdine was used as fluorescent sensor to correlate P. aeruginosa contamination to infection. The TelM platform was validated with environmental waterborne microbes from marine samples. Overall, the TelM platform can be readily applied to assess microbial and chemical risk in aquatic bodies in resource-constrained settings.

Biomarker barcodes: multiplexed microfluidic immunohistochemistry enables high-throughput analysis of tissue microarray

We present a multiplexed microfluidic immunohistochemistry (IHC) technology that enables high-throughput analysis of tissue microarrays (TMAs) using the patterns of biomarker barcodes, which consist of a series of expressed linear patterns of specific biomarkers. A multichannel poly(dimethylsiloxane) microfluidic device was reversibly assembled by the pressure of simple equipment for multiplexed IHC on each core of TMA or cell microarray (CMA) section slides. By injecting primary antibodies from different biomarkers independently into each channel, multiplexed immunostaining can be performed on each core of TMA. We confirmed the equal immunostaining quality regardless of the channel orders and core positions in the slide. Four different biomarkers (ER, PR, HER2, and Ki67) were used for the demonstration of distinctive expression patterns on CMAs which consist of six different breast cancer cell lines, and it was confirmed that these bar-like signals could be a biomarker barcode for the TMA core. A biomarker barcode of breast cancer patient-derived TMA was quickly scanned by a slide scanner and compared to the conventional method for breast cancer diagnosis. This "barcode-IHC" concept, which has been verified by performing multiplexed microfluidic IHC on CMA and TMA samples, provides high reproducibility and the potential of high-throughput screening with molecular diagnostic capability.

Recent technical advances in whole slide imaging instrumentation

Microscopic observation of biological specimen smears is the mainstay of diagnostic pathology, as defined by the Digital Pathology Association. Though automated systems for this are commercially available, their bulky size and high cost renders them unusable for remote areas. The research community is investing much effort towards building equivalent but portable, low-cost systems. An overview of such research is presented here, including a comparative analysis of recent reports. This paper also reviews recently reported systems for automated staining and smear formation, including microfluidic devices; and optical and computational automated microscopy systems including smartphone-based devices. Image pre-processing and analysis methods for automated diagnosis are also briefly discussed. It concludes with a set of foreseeable research directions that could lead to affordable, integrated and accurate whole slide imaging systems.

Preclinical models and technologies to advance nanovaccine development

The remarkable success of targeted immunotherapies is revolutionizing cancer treatment. However, tumor heterogeneity and low immunogenicity, in addition to several tumor-associated immunosuppression mechanisms are among the major factors that have precluded the success of cancer vaccines as targeted cancer immunotherapies. The exciting outcomes obtained in patients upon the injection of tumor-specific antigens and adjuvants intratumorally, reinvigorated interest in the use of nanotechnology to foster the delivery of vaccines to address cancer unmet needs. Thus, bridging nano-based vaccine platform development and predicted clinical outcomes the selection of the proper preclinical model will be fundamental. Preclinical models have revealed promising outcomes for cancer vaccines. However, only few cases were associated with clinical responses. This review addresses the major challenges related to the translation of cancer nano-based vaccines to the clinic, discussing the requirements for ex vivo and in vivo models of cancer to ensure the translation of preclinical success to patients.

FRACTAL: Signal amplification of immunofluorescence via cyclic staining of target molecules

In this article, we demonstrate fluorescent signal amplification via cyclic staining of target molecules (FRACTAL), a technique that can amplify the signal intensity of immunofluorescence staining more than nine-fold via simple cyclic staining of secondary antibodies. We also show that FRACTAL is compatible with four-color imaging and expansion microscopy imaging.

An integrated microfluidic system for rapid, automatic and high-throughput staining of clinical tissue samples for diagnosis of ovarian cancer

Accurate cancer diagnostic methods are of urgent need. Since traditional immunohistochemistry (IHC)-based approaches, while reliable, are labor-intensive and require well-trained technicians, we developed an integrated microfluidic platform capable of labeling ovarian cancer biomarkers (i.e. aptamer) within formalin-fixed, paraffin embedded tissues via molecular probes. Both aptamer-based 1) fluorescent staining and 2) IHC staining of clinical tissue samples could be automated in the microfluidic system in only 2-3 h (40-50% faster than conventional approaches) with <0.5 mL of reagents, signifying that this device could serve as a promising diagnostic tool for ovarian cancer.

A 3D mixing-based portable magnetic device for fully automatic immunofluorescence staining of γ-H2AX in UVC-irradiated CD4+ cells

Immunofluorescence (IF) is a common method used in cell biology. The conventional protocol for IF staining is time and labor-intensive, operator dependent and reagent-consuming. Magnetic Bead (MB)-based microdevices are frequently utilized in cellular assays, but integration of simple and efficient mixing with downstream multi-step manipulation of MBs for automatic IF staining is still challenging. We herein present a portable, inexpensive and integratable device for MB-based automatic IF staining. First, a front-end cell capture step is performed using a 3D-mixing module, which is built upon a novel mechanism named ec-2MagRotors and generates periodically changing 3D magnetic fields. A 5-fold enhancement of cell capture efficiency was attained even with a low bead-to-cell concentration ratio (5 : 1), when conducting magnetic 3D mixing. Second, a 1D-moving module is employed downstream to automatically manipulate MB–cell complexes for IF staining. Further, a simplified protocol for staining of γ-H2AX, a biomarker widely used in evaluation of cell radiation damage, is presented for proof-of-principle study of the magnetic device. Using UVC-irradiated CD4⁺ cells as samples, our device achieved fully automatic γ-H2AX staining within 40 minutes at room temperature and showed a linear dose–response relationship. The developed portable magnetic device is automatic, efficient, cost-effective and simple-to-use, holding great potential for applications in different IF assays.

A 3D mixing-based portable magnetic device to perform on-chip efficient cell capture and automatic intracellular immunofluorescence (IF) staining is presented.

Microfluidics-assisted multiplexed biomarker detection for in situ mapping of immune cells in tumor sections

Because of the close interaction between tumors and the immune system, immunotherapies are nowadays considered as the most promising treatment against cancer. In order to define the diagnosis and the subsequent therapy, crucial information about the immune cells at the tumor site is needed. Indeed, different types or activation status of cells may be indicative for specific and personalized treatments. Here, we present a quantitative method to identify ten different immuno-markers in the same tumor cut section, thereby saving precious samples and enabling correlative analysis on several cell families and their activation status in a tumor microenvironment context. We designed and fabricated a microfluidic chip with optimal thermomechanical and optical properties for fast delivery of reagents on tissue slides and for fully automatic imaging by integration with an optical microscope. The multiplexing capability of the system is enabled by an optimized cyclic immunofluorescence protocol, with which we demonstrated quantitative sequential immunostaining of up to ten biomarkers on the same tissue section. Furthermore, we developed high-quality image-processing algorithms to map each cell in the entire tissue. As proof-of-concept analyses, we identified coexpression and colocalization patterns of biomarkers to classify the immune cells and their activation status. Thanks to the quantitativeness and the automation of both the experimental and analytical methods, we believe that this multiplexing approach will meet the increasing clinical need of personalized diagnostics and therapy in cancer pathology.

Advances in diagnostic microfluidics

Microfluidics is an emerging field in diagnostics that allows for extremely precise fluid control and manipulation, enabling rapid and high-throughput sample processing in integrated micro-scale medical systems. These platforms are well-suited for both standard clinical settings and point-of-care applications. The unique features of microfluidics-based platforms make them attractive for early disease diagnosis and real-time monitoring of the disease and therapeutic efficacy. In this chapter, we will first provide a background on microfluidic fundamentals, microfluidic fabrication technologies, microfluidic reactors, and microfluidic total-analysis-systems. Next, we will move into a discussion on the clinical applications of existing and emerging microfluidic platforms for blood analysis, and for diagnosis and monitoring of cancer and infectious disease. Together, this chapter should elucidate the potential that microfluidic systems have in the development of effective diagnostic technologies through a review of existing technologies and promising directions.

Microfluidic-Based Platform for the Evaluation of Nanomaterial-Mediated Drug Delivery: From High-Throughput Screening to Dynamic Monitoring

Nanomaterial-based drug delivery holds tremendous promise for improving targeting capacity, biodistribution, and performance of therapeutic/diagnostic agents. Accelerating the clinical translation of current nanomedicine requires an in-depth understanding of the mechanism underlying the dynamic interaction between nanomaterials and cells in a physiological/pathophysiological-relevant condition. The introduction of the advanced microfluidic platform with miniaturized, well-controlled, and high-throughput features opens new investigation and application opportunities for nanomedicine evaluation. This review highlights the current state-of-theart in the field of 1) microfluidic-assisted in vitro assays that are capable of providing physiological-relevant flow conditions and performing high-throughput drug screening, 2) advanced organ-on-a-chip technology with the combination of microfabrication and tissue engineering techniques for mimicking microenvironment and better predicting in vivo response of nanomedicine, and 3) the integration of microdevice with various detection techniques that can monitor cell-nanoparticle interaction with high spatiotemporal resolution. Future perspectives regarding optimized on-chip disease modeling and personalized nanomedicine screening are discussed towards further expanding the utilization of the microfluidic-based platform in assessing the biological behavior of nanomaterials.

On-chip immunofluorescence analysis of single cervical cells using an electroactive microwell array with barrier for cervical screening

Several specific tests for cervical screening have been developed recently, including p16/Ki67 dual immunostaining for diagnosing high-risk human papillomavirus positive squamous intraepithelial lesion in the cervix. However, manual screening of cells in an entire glass slide is currently a standard clinical procedure for quantification and interpretation of immunocytochemical features of the cells. Here, we developed a microfluidic device containing an electroactive microwell array with barriers (EMAB) for highly efficient single-cell trapping followed by on-chip immunofluorescence analysis with minimum loss of the sample. EMAB utilizes patterned electrodes at the bottom of cell-sized microwells to trap single cells using dielectrophoresis (DEP) and cell-holding structures behind the microwells to stabilize the position of trapped cells even without DEP. Using the device, we evaluated the performance of p16/Ki67 dual immunostaining of HeLa cells on the chip. The device shows 98% cell-trapping efficiency as well as 92% cell-holding efficiency against the fixed HeLa cells, and we successfully demonstrated high-efficiency on-chip immunofluorescence analysis with minimal loss of sample. p16/Ki67 dual immunostaining using EMAB may be useful for complementary tests for cervical screening in confirming the histopathological diagnosis.

Finger-Actuated Microfluidic Concentration Gradient Generator Compatible with a Microplate

The generation of concentration gradients is an essential part of a wide range of laboratory settings. However, the task usually requires tedious and repetitive steps and it is difficult to generate concentration gradients at once. Here, we present a microfluidic device that easily generates a concentration gradient by means of push-button actuated pumping units. The device is designed to generate six concentrations with a linear gradient between two different sample solutions. The microfluidic concentration gradient generator we report here does not require external pumps because changes in the pressure of the fluidic channel induced by finger actuation generate a constant volume of fluid, and the design of the generator is compatible with the commonly used 96-well microplate. Generation of a concentration gradient by the finger-actuated microfluidic device was consistent with that of the manual pipetting method. In addition, the amount of fluid dispensed from each outlet was constant when the button was pressed, and the volume of fluid increased linearly with respect to the number of pushing times. Coefficient of variation (CV) was between 0.796% and 13.539%, and the error was between 0.111% and 19.147%. The design of the microfluidic network, as well as the amount of fluid dispensed from each outlet at a single finger actuation, can be adjusted to the user’s demand. To prove the applicability of the concentration gradient generator, an enzyme assay was performed using alkaline phosphatase (ALP) and para-nitrophenyl phosphate (pNPP). We generated a linear concentration gradient of the pNPP substrate, and the enzyme kinetics of ALP was studied by examining the initial reaction rate between ALP and pNPP. Then, a Hanes–Woolf plot of the various concentration of ALP was drawn and the V_max and K_m value were calculated.

Combining fluorescence-based image segmentation and automated microfluidics for ultrafast cell-by-cell assessment of biomarkers for HER2-type breast carcinoma

Immunohistochemistry (IHC) is one of the main clinical techniques for biomarker assessment on tissue biopsies. It consists in chromogenic labeling with specific antibodies, followed by optical imaging, and it is used for diagnosis and therapeutic targeting. A well-known drawback of IHC is its limited robustness, which often precludes quantitative biomarker assessment. We combine microfluidic immunostaining, fluorescence imaging, and image-based cell segmentation to create an ultrafast procedure for accurate biomarker assessment via IHC. The experimental protocol is very simple and based on fast delivery of reagents in a microfluidic chamber created by clamping a half-chamber patterned in a silicon chip on top of a tumor tissue section. Also, the imaging procedure simply requires a standard fluorescence microscope, already widely used in clinical practice. The image processing is based on local-contrast enhancement and thresholding of the obtained fluorescence image, with subsequent Voronoi segmentation. To assess the experimental and analytical procedure on robust biological controls, we apply our method to well-characterized cell lines, which guarantee higher reproducibility than whole-tissue samples and therefore enable to disentangle the technical variability from the biological variability. To increase the potential translationality, we address the detection and quantification of the human epidermal growth factor receptor 2 (HER2) protein, which is a biomarker for HER2-type breast carcinoma diagnosis and therapy. We report both ultrafast immunofluorescence staining (5 min per sample) of two breast cancer biomarkers and ultrafast cell segmentation (1 min per sample = processing of thousands of cells). This provides a quantitative, cell-based immunofluorescent signal, with which we propose a potential diagnostic criterion to separate HER2-positive and HER2-negative breast cancer cells at high sensitivity and specificity.

Microfluidic on-chip immunohistochemistry directly from a paraffin-embedded section

We present here a novel microfluidic platform that can perform microfluidic on-chip immunohistochemistry (IHC) processes on a formalin-fixed paraffin-embedded section slide. Unlike previous microfluidic IHC studies, our microfluidic chip made of organic solvent-resistant polyurethane acrylate (PUA) is capable of conducting on-chip IHC processes consecutively. A narrow channel wall structure of the PUA chip shows effective sealing by pressure-based reversible assembly with a section slide. We performed both on-chip IHC and conventional IHC processes and compared the IHC results based on the immunostaining intensity. The result showed that the effects of the on-chip deparaffinization, antigen retrieval, and immunoreaction processes on the IHC result were equivalent to conventional methods while reducing the total process time to less than 1/2. The experiment with breast cancer tissue shows that human epidermal growth factor receptor 2 (HER2) classification can be performed by obtaining a clearly distinguishable immunostaining intensity according to the HER2 expression level. We expect our on-chip microfluidic platform to provide a facile technique suitable for miniaturized, automated, and precise diagnostic devices, including a point-of-care device.